I think that all of the characters Hayou Mizaki (forgive me if I spelled that wrong) creates connect to a certain part of you. Mei connects to the child within you, Chihiro connects to your mysterious part of you, and Arieyette connects to your curiosity. I think the characters is what makes these movies so great. They are relatable, funny, and all around great. When I first started watching anime, I was really little. Dragon ball Z and Ponyo were my favorite things ever. And sure I get crap about being a geek, but during some hard periods in my life, Ponyo and Ariyetta and Totoro helped me escape to the world of ghibli. Making me happy. I think that is why I'm in love with it. Oops. I ranted sorry.
:D Chemical Days mentions great characters. They are all good and they are somehow connected to our inner hearth. By the way Arrietty is from Hiromasa Yonebashi.
I wouldn't say Chihiro is connected to our mysterious part (the movie does). She is kind of inexperienced, anxious, but she is also helpful. She lives in a dangerous world, like many teenagers today are anxious of the future.